im 22 yrs old and im experiencing a very irregular monthly period..sometimes it took 40 days, meaning there are months when i don't have my period and sometimes its only 28 days..how could i possibly have a normal cycle?? is being sexually active a cause of the abnormality?? tnx..pls help me.

I don't think that sexual activity can control the cycle's regularity. Menstrual irregularity is not a disease per se, though it could be a sign of other diseases. But since it is quite common among the general mass, investigating it would be usually done only after a trial of medications. Oral contraceptives are the first line of medications that are used to regularize menses.